Given the range of reactions to the challenge, researchers wanted to know which countries were managing their ageing populations best. Researchers led by John Rowe of Colombia University devised a new way to measure the wellbeing of older people in 30 countries.

How did they rank countries?

The researchers came up with a measure called the Hartford Index, which considers:

Productivity and engagement: how much older people are connected within and outside the workforce

Wellbeing: how healthy and happy older people are

Equity: the size of the inequalities between well-off and deprived parts of the elderly population

Cohesion: how socially connected older people are

Security: how well supported people were in their retirement, as well as their physical safety

"The index provides an accurate look at how well societies are adapting to this ageing challenge," said Dana Goldman of the University of Southern California's Schaeffer Center for Health Policy and Economics, who is presenting the findings at a meeting of the International Association of Gerontology and Geriatrics in San Francisco.

Taking all this into account, Norway came out with the highest score, at 65 out of 100. It was closely followed by Sweden at 62, the US at 59.8 and the Netherlands at 59.5. The UK scored a not very impressive 51.9, sandwiched between Spain at 52.7 and Austria at 50.4.

The scale comes out with different results to the rankings by the Global AgeWatch Index, which was last updated in 2015. According to that measure, Switzerland comes out on top, followed by Norway, Sweden and Germany. On that list, the US ranks just 9th in the world, followed by the UK in 10th place.

"Now that previously unimagined numbers of older persons are living longer it is critical that we shift from our prior sole focus on the characteristics of individuals and their immediate environments to one that includes a strategy for the entire society to successfully adapt to an ageing population," said Rowe.

The researchers hope that the findings can help inform policies to tackle the challenges of an increasingly elderly population proactively.

"Failure to adapt to aging is a risky strategy for a country," said Rowe. "The good news is this gloomy scenario is avoidable."

Norway tops the list of 30 countries, the top 18 of which are listed here.John A. Hartford Foundation Index of Societal Aging